F(x)={sinx for x<22/7 {mx+b for x>22/7

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Discussion Overview

The discussion revolves around finding the values of the constants b and m for the piecewise function defined as f(x)={sin x for x=pi. Participants explore the conditions under which this function is continuous and differentiable at x=pi.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested, Homework-related

Main Points Raised

  • One participant initially presents a function but does not specify the conditions for differentiability, leading to a correction regarding the need for continuity at x=pi.
  • Another participant emphasizes that for the function to be differentiable at x=pi, it must first be continuous, stating that the limits from both sides must match.
  • The continuity condition is expressed as mπ + b = sin(π) = 0.
  • For differentiability, it is proposed that m must equal cos(π) = -1.
  • A later post clarifies the problem statement, confirming that the function is indeed defined for x=pi.
  • Participants discuss the implications of these conditions without reaching a consensus on the values of m and b.

Areas of Agreement / Disagreement

Participants generally agree on the need for continuity and differentiability at x=pi, but there is no consensus on the specific values of m and b, as the discussion remains open-ended.

Contextual Notes

There are unresolved assumptions regarding the definitions of continuity and differentiability, as well as the specific values of the constants m and b based on the conditions discussed.

kidia
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Hi any idea on this:
Find all the values of the constants b and m for which the function.

f(x)={sinx for x<22/7
{mx+b for x>22/7

I will appreciate for any help
 
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Rule 1: Copy the problem correctly! The way you've stated it, you can't find m and b. There exist functions having those values for all m and b! Did you mean "for which the function,..., IS DIFFERENTIABLE at x= 22/7"?

In order to be differentiable at a point, the function must first be continuous there.
Strictly speaking, the function you gave is not even defined at 22/7 and so can't be continuous there.

I am going to assume that what you REALLY mean is: "Find all values of the constants b and m for which the function
{sin x for x<= 22/7
f(x)= { mx+ b for x> 22/7

is differentiable." (Since f is clearly differentiable every where other than 22/7 the crucial part is that it be differentiable at 22/7).

In order to be differentiable, it must first be continuous: the limit of f(x) at 22/7 FROM THE LEFT (x< 22/7) is sin(22/7) (And, once again: 22/7 is ALMOST pi. Did your problem really have 22/7 rather than pi). The limit of f(x) at 22/y FROM THE RIGHT is
22m/7+ b so we must have 22m/7+ b= sin(22/7) (which is close to 0).

The derivative of f, for x< 22/7 is cos(x). The derivative of f for x> 22/7 is m. While it is not necessary that derivatives be continuous, they do satisfy the "intermediate value problem" so if f is differentiable at 22/7, and since the derivative functions to the left and right of 22/7 are continuous, they must "match up" there: m= cos(22/7) (close to -1). You can put that into the other equation to solve for b. (In fact, mx+ b is simply the tangent line to sin(x) at x= 22/7.)
 
sorry,sorry,sorry is true the one sent to me copied the problem wrong is like this

Find all the values of the constants b and m for which the function.

f(x)={sin x for x<pi
{mx+b for x>=pi
is a)continuous at x=pi b)is differentiable at x=pi
 
Okay- in order fror the function to be continuous at pi, we must have
[tex]m\pi+ b= sin(\pi)= 0[/tex]
In order for the function to be differentiable at pi, we must also have
[tex]m= cos(\pi)= -1[/tex].
 
Thanx I understand u
 

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